If the friction increase it would make the thing sliding down slower and makes heat
The aspect of his fitness program that could keep the young man from achieving his goal would potentially be the exercise with his friend. His friend could be a hindrance to his motivation to do more or to continue. If he's so attached with exercising with his friend and his friend decides to stop, then he would probably lose motivation.
Using the equation σ =K/(Y √π a) ; a=1/π (K/Yσ)^2. The critical stress required for initiating crack propagation is σ, plain strain fracture toughness is K, surface length of the crack is a, and dimensionless parameter us Y.Substituting the given parameters to the equation. 82.4 MPa √m for K, 345 MPa for σ, and 1 for Y in the equation of surface length of the crack.a = 1/π (K / Yσ )^2 = 1/π (82.4 / 1*345 )^2 = 0.01815 m= 18.15mm
